Cable strap with multiple tooth pawl

ABSTRACT

The cable strap or tie disclosed has an elongated, unitary, flexible plastic strap body with an enlarged head at one end. A transverse opening in the head allows the strap body or tongue to be threaded through the opening in the head to clamp a bundle of wires or the like within the loop so formed. At the head end the tongue terminates in an integral flexible pawl disposed in the passage through the head opening. The pawl has adjacent to its free end a plurality of stub end ratchet teeth positioned to mate with the strap body when the tongue of the cable strap is threaded through the head. The pawl has a tapered body leading to the tooth alignment. The alignment of teeth may include two, three or four teeth, the most remote tooth terminating a distance below the plane of the top of the head by at least one tooth spacing.

United States Patent Morgan Oct. 2, 1973 [54] CABLE STRAP WITH MULTIPLETOOTH 3,660,869 5/1972 Caveney et al. 24/16 PB PAWL P E D ld A G 'ffrzmary xammer ona n in [75] Inventor. Thomas Edward Morgan, ClevelandAtt0mey C Come Remsen JR et aL Heights, Ohio [73] Assignee:International Telephone and [57] ABSTRACT Telegraph 119F890", New YorkThe cable strap or tie disclosed has an elongated, unitary, flexibleplastic strap body with an enlarged head [22] Filed: 20, 1971 at oneend. A transverse opening in the head allows the Appl. No.: 209,921

strap body or tongue to be threaded through the opening in the head toclamp a bundle of wires or the like within the loop so formed. At thehead end the tongue terminates in an integral flexible pawl disposed inthe' passage through the head opening. The pawl has adjacent to its freeend a plurality of stub end ratchet teeth positioned to mate with thestrap body when the tongue of the cable strap is threaded through thehead. The pawl has a tapered body leading to the tooth alignment. Thealignment of teeth may include two, three or four teeth, the most remotetooth terminating a distance below the plane of the top of the head byat least one tooth spacing.

5 Claims, 5 Drawing Figures CABLE STRAP WITII MULTIPLE TOOTH PAWLBACKGROUND OF THE INVENTION The invention relates to a cable strap(sometimes called a bundle tie) adapted to be fabricated as an integralone-piece structure.

The prior art is replete with many forms of cables embodying manyvariations in component shape and size. Some employ integral one-piececonstruction including a pawl extending into the head opening, whileothers use metal pawls embedded in the strap and protruding into theopening. Many variations in the shape of the pawl have been used as thebasis for patents, either alone or in combination with the shape ofratchet teeth on the body or tongue of the strap. For example, in my US.Pat. No. 3,672,003 issued June 27, 1972, I show a strap of generallysimilar construction having a single tooth at the pawl end.

The ideal cable strap would be a low cost strap capable of beingfabricated by mass production techniques and which reliably and tightlyclamps and holds a wire or group of wires within the strap loop in amanner allowing ready assembly of the tie and one which can withstandbending forces and shear forces.

To approach this ideal, the present invention utilizes a unitaryconstruction with a pawl inherently molded to the end of the tongue orbody within the head; the pawl is relatively flexible and its joinder tothe strap body is arcuate. The pawl body is substantially normal to thetongue body and terminates in either two, three or four spaced ratchetpawl teeth, the outermost end of the upper tooth forming the pawl tip.The teeth mate with similarly shaped ratchet teeth formed in the strapbody when the strap body has passed through a passage in the head. Thestrap is held firmly and tightly by this mating, with the side risers ofthe passage binding the strap to the pawl thereby locking the cablebundle within the strap loop. The strap head is essentially a U- shapedmember integrally connected to the strap body, with the base of theU-shape confronting the pawl, and with the pawl extending into the Uopening beyond the partial riser walls of the head. The strap may haveits outer sidewalls beveled to approximate a hexagonal form.

SUMMARY OF THE INVENTION My pawl is arcuate, thinner than the thicknessof the strap, and tapers from a maximum thickness where it joins theteeth to a minimum thickness immediately adjacent to the first pawltooth. Most other multiple tooth pawls are thicker than the strapthickness and have a narrowed cross section acting as a hinge or pivotat, the base of the pawl. My pawl flexes throughout its length and,therefore, does not have excessively high stress concentrations in anyone specific area as the other pawls frequently have at their pivotsection. It is well known in the art that a tapered cantilever beam suchas my pawl is a more or less "constant strength cantilever beam, therebeing no one area of weakness where breakage is more apt to occur. Thecurved shape of my pawl allows a gradual transition from the strap tothe pawl teeth which again keeps stress concentrations to a minimum.Most other pawl designs are attached to a wall rather than directly tothe strap. Most other designs have a notch between the pawl and thewall. It is well known in the art that a notch causes a very high stressconcentration, which my design avoids.

My design employs a plurality of ratchet teeth. In the course ofdeveloping a single-tooth pawl, I found that for small cable straps asingle tooth was not strong enough. The single tooth tended to abradedue to its engaging teeth on the strap and thereby causing the pawl todeform and allow the strap to slip. By adding at least one additionaltooth, this deformation of the teeth is essentially prevented. Also,when ratcheting a long strap past the pawl, the lower most tooth absorbssubstantially all the wear and abrasion. The other tooth or teeth arepivoted away from engagement with the strap during its passage throughthe pawl opening in the forward direction leaving the top tooth or teethunabraded, which is important since the top tooth or teeth support mostof the load. A single tooth would naturally wear down when ratcheting along strap past it and might not be capable of supporting the fullnormal load. By the addition of further teeth, these teeth will engageand hold the strap teeth against release.

It is therefore the major object of my invention to provide a new andimproved one-piece cable strap.

It is a still further object of my invention to provide a new one-piececable strap with integrally formed, multiple tooth, flexible pawl ofnovel configuration.

It is a still further object of my invention to provide a cable strapwith a new and improved head design.

Other objects, features and advantages of the invention will become moreapparent from the following specification and claims taken inconjunction with the drawings, the description of which follows.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view in elevation ofa preferred embodiment of a cable strap employing my invention;

FIG. 2 is a sectional view of the strap of FIG. 1, taken along line 2-2of FIG. 1;

FIG. 3 is a side view in elevation of the head end of the cable strap;

FIG. 4 is an enlarged sectional view of a head and pawl where the pawlhas three teeth, and;

FIG. 5 is a view similar to FIG. 4 of a further embodiment of myinvention having four teeth.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The cable tie or strap 10shown in the drawings may be provided in a number of lengths and widths,however, the comparative shapes and relationship of the component partsthereof are generally maintained. Strap 10 includes a main body 12 andan enlarged head 14 connected at one end thereof. The cable tieincluding both body and head preferably is molded as a unitary member ofmaterial such as nylon or suitable flexible but somewhat rigid plasticmaterial such as polypropylene. The main body 12 is of-generallyrectangular or oblong cross section with parallel sides 20 terminatingat its free end in a tongue 22 which may be arcuate as shown, or taperedas desired.

The body 12 as shown in FIG. 2 may be comparatively flat for a portion24 of its length nearest head 14. From this fiat portion 24, the body 12is sloped within a ramp portion 26 which terminates in an offset orstepped portion 28 adjacent tongue end 22. This offset makes it easierto push the strap 10 under a bundle of wires while considerablylessening the risk of the strap being caught within the bundle itself.

The top surface 30 of body 12 (as best seen in FIGS. l and 2) has aseries of serrations 32 which in the form shown extend throughout theoffset portion 28. If desired, the extent of the serrations 32 maycontinue for some of the ramp portion 26. One purpose ofthe serrationsis to allow the offset portion 28 to be grasped manually for looping orthreading of the tongue end through the head. The serrations are boundedby the strap edges 34 at each side 20 of the main body 12, and the rootsof the serrations substantially coplanar with the surface 30 and rails34. These serrations also serve as a temporary means of holding a strapto a bundle of wires prior to tightenting, by engaging the inside topedge 36 of head 14. When this edge is engaged, the strap will notstraighten out and will not fall off the bundle, however, the strap caneasily be removed by the application of a slight force.

As best seen in FIG. 2, the body under-surface 40 has ratchet teethindicated by reference characters 42 and 44 incised into the surface forthe longitudinal extent of which may be varied from strap to strap, asdesired. Once the strap has been pulled taut through head 14, the mainstrap teeth 42 and 4 5 are fully engages by the pawl, the strap cannotbe removed except by cutting, or prying the pawl open with a sharpobject such as the tip of a knife blade.

The enlarged head 14 includes a U-shaped main framing member 50 archedabout and defining an oblong aperture 52 which extends entirely throughthe body of the cable strap. The framing member 50 has an end wall 54normal to the main body 12, the end wall on its outer surface merginginto tapered or substantially hexagonal side walls 56 angularly disposedoutwardly of the strap body sides 20. The side walls 56 terminate insymmetrical imposts 58 on each side of the oblong aperture. The impostsdefine one longitudinal edge of the oblong aperture, the impoststerminating in interior shoulders 60 parallel to the side 20 of the mainbody, such that the impost walls 64 form a passageway and support for atongue passing through the aperture.

Within the oblong aperture, as best seen in FIGS. 1 and 2, the main body12 of the strap has an extension in the form of pawl 70. Pawl 70 is Fsomewhat lesser thickness than the tongue body 12 and is angledgenerally rectangularly from the tongue body. The joinder of the pawl tothe tongue end is essentially radial to lessen stress coplanar with twospaced apart ratchet teeth 75, the upper edge of the uppermost of theseteeth forming an edge surface or pawl tip 76.

The body of pawl 70 is separated laterally from the impost walls 60 bylateral spacings 86, with the pawl being connected only to the strapbody. The pawl teeth 75 intrude into the aperture 52 within the framedhead and may pivot or flex as a strap passes through the aperture 52.

Functionally, the longitudinal depth of aperture 52 is slightly greaterthan the thickness of the main body to provide clearance for the tongueend of the body to be looped through the head aperture with the bodyundersurface 40 adjacent the pawl teeth 75. The impost walls 64 tend toguide the main strap body through the aperture and tend to align thestrap body with respect to pawl 70. The end wall d of the framing memberalso acts to support and guide the tongue end 22 as it passes throughthe aperture.

In use, the tongue end 22 is passed through the aperture until theserrated portion has cleared the aperture so that the tongue endserrations may be grasped manually. The tongue end can then be pulledthrough until the ratchet teeth 42 can mate with pawl teeth and lock thecable strap around the object or objects held within the loop thereof,in generally-known fashion. With the tongue end of the strap body loopedthrough the head, the pawl remains within the area bounded by theimposts and head remote end by a distance greater than one pawl tooth toprevent shearing of a tooth on the tongue which would otherwise engagethe pawl teeth. It is understood that such straps are normally tightenedby a tensioning tool which pulls the strap through the head to apredetermined or settable tension. The strap is cut and may slide backby a nominal distance on release of the tool applied tension. In thenormal usage for which the strap is intended, a bundle of wires will beheld within the loop so formed so that the wires may be held tightlyagainst one another in a substantially permanent bundle.

The pawl 70, as shown, comprises an extension of the end of the mainstrap body 12 with the pawl being tapered or narrower in cross sectionprogressively. The pawl body permits longitudinal flexure and pivotalmovement of the pawl as the strap end is threaded therethrough. The pawlbody provides the section of least thickness and maximum flexibility inthe area just below the lower one of teeth 75. Each tooth has a taperedlower surface and an upper edge substantially normal to the pawl bodywith the tip end of each tooth being blunted, the blunt tip of the toothis designed to complement the shape of the strap teeth. The upper tooth76 is similarly shaped with its upper edge copla nar with the pawl tip.The taper of the pawl tooth lower surface relative to the opposedheadwall 91 is typically about 35 to permit passage of the body andproper flexure of the pawl. The lower tooth will typically contact thestrap body during passage while the upper tooth 76 will aid in retainingthe strap in place once its proper position has been reached. Both teethremain well within the head at all times, the upper tooth tip 76 beingrecessed by at least 0.030 to 0.050 inches from the top of the head atall times to prevent accidental cut-off of a working portion of thestrap when the strap is tensioned about a bundle of wires and the strapend cut off flush with the head.

The embodiment of FIG. 4 covers a strap I01 which for the most part isidentical to the embodiment of FIG. 2. The pawl 102 of FIG. 4 differsfrom that of FIG. 2 in that there are three pawl teeth 104 within thesame vertical extent as the two teeth of FIG. 2. The teeth 104 areshallower in depth than those of FIG. 2, and are regularly spaced withinthe toothed extent. As can be seen in FIG. 4, the root dimension of eachtooth 104 provides a flat area 106 between each tooth, the pawl teeth104 being suitably blunted to mate accordingly with the strap bodyteeth.

In FIG. 5, I show a cable tie 111, generally similar to those previouslyshown, cable tie 111 housing a pawl 112 with four equally spaced teeth114. Teeth 114 are confined within the same vertical extent as those ofthe prior embodiment. Each tooth has a blunted tip 116 of short verticalextent and an acutely angled root 118.

In using any of the cable ties shown, the tongue end is looped about acable tie and threaded through the opening and the end is pushed throughthe head past the plane of the top of the head. The tongue end isgrasped and pulled further through the head. The

tongue end may be inserted into a strap tensioning tool and pulled tautwith the tool actuated force.

As the tongue end passes the pawl, the lowermost tooth is engaged and ispivoted to further open the head opening. The remote end of the pawl ispivoted out of the way of the passing tongue so that only the lowermosttooth is abraded by the ratcheting of the tongue past the pawl. Theremaining teeth being clear of the tongue during its passage, remainrelatively unaffected by the tongue.

We have found that by inclining the bottommost tooth at an angle ofabout 35 relative to the opposite wall 91 of the opening, theinclination of the pawl to allow passage of the tongue is limited to anextent clearly within the bending range of the pawl material without thecreation of crack-producing stresses within the pawl pivoting area.

Of course, the distance between the plane through the tips of the teethand the opposed wall of the head opening is less than the nominalthickness of the tongue so that the pawl teeth will interfere with thefree passage of the tongue. The interference may be in the range of0.006 to 0.010 inches for three or four tooth pawls and slightly greaterfor the two toothed pawl.

In no event is the interference greater than the thickness of the pawlbody behind the teeth, and should be maintained at a comparatively lowvalue so that the pawl is not greatly pivoted on the ratcheting of astrap tongue past the pawl teeth.

What I claim is:

1. A cable strap of unitary construction comprising an elongated body ofgenerally rectangular cross section with an enlarged head connected toone end of said strap, there being a passage through said head adaptedto receive the looped remote end of the strap to form a loop for holdingobjects therein, the invention wherein within said head passage there isan elongated, flexible pawl integrally and curvedly connected to saidstrap and extending freely into said passage between the sidewalls, thebody of said pawl comprising an extension of the strap narrowing inthickness from the thickness of the strap at its pivotal connectionthereto, an alignment of ratchet teeth incised into one face of thestrap adjacent the remote end of said strap and a first tooth and secondtooth on said pawl protruding normally into the passage confronting theend wall of the head and spaced in the path of the looped end of saidstrap the first of said teeth positioned to cause flexure of said pawlbody as the tooth matingly engages said ratchet teeth as the remote endof the strap body is threaded through the passage in said head, thesecond of said teeth positioned to be moved away from strap remote endduring said threading and to restore and hold the strap remote endagainst the end wall of said head when fully looped through the head.

2. A cable strap as claimed in claim 1, wherein the teeth on the pawlhave their tips blunted to mate with like spacings between the ratchetteeth in the strap face.

3. A strap as claimed in claim 1, wherein said pawl has side walls whichtaper toward convergence adjacent the first of said two teeth.

4. A strap as claimed in claim 1, wherein there is a third tooth on saidpawl positioned intermediate between said first and second tooth.

5. A cable strap of unitary construction comprising an elongated body ofgenerally rectangular cross section having ratched teeth with anenlarged head connected to one end of said strap, there being a passagethrough said head adapted to receive the looped end of the strap to forma loop for holding objects therein, the invention wherein within saidhead passage there is an elongated, flexible pawl integrally andcurvedly connected to said strap and extending freely into saidsidewalls, the body of said pawl comprising a smoothly curvedconcave-convex member of generally decreasing cross section and at leasta lower and upper tooth protruding from said pawl body adjacent the freeend thereof, said teeth spaced along said passage and spaced from andconfronting the end wall of the head, said pawl tapering from itsconnection to the strap to a narrowed section adjacent the lower of saidteeth, said pawl adapted to be flexed by said strap end to remove theupper tooth from contact with said strap end during movement of saidstrap through said head passage and said lower tooth protrusive fromsaid narrowed section to matingly engage said ratchet teeth as theremote end of the strap body is threaded through the passage, said uppertooth aligned to restore from said flexed position at the termination ofmovement of said strap through said passage, said upper tooth alignedopposite said end wall to restrain said strap against said end wall toprevent withdrawal of said strap from said passage.

1. A cable strap of unitary construction comprising an elongated body ofgenerally rectangular cross section with an enlarged head connected toone end of said strap, there being a passage through said head adaptedto receive the looped remote end of the strap to form a loop for holdingobjects therein, the invention wherein within said head passage there isan elongated, flexible pawl integrally and curvedly connected to saidstrap and extending freely into said passage between the sidewalls, thebody of said pawl comprising an extension of the strap narrowing inthickness from the thickness of the strap at its pivotal connectionthereto, an alignment of ratchet teeth incised into one face of thestrap adjacent the remote end of said strap and a first tooth and secondtooth on said pawl protruding normally into the passage confronting theend wall of the head and spaced in the path of the looped end of saidstrap the first of said teeth positioned to cause flexure of said pawlbody as the tooth matingly engages said ratchet teeth as the remote endof the strap body is threaded through the passage in said head, thesecond of said teeth positioned to be moved away from strap remote endduring said threading and to restore and hold the strap remote endagainst the end wall of said head when fully looped through the head. 2.A cable strap as claimed in claim 1, wherein the teeth on the pawl havetheir tips blunted to mate with like spacings between the ratchet teethin the strap face.
 3. A strap as claimed in claim 1, wherein said pawlhas side walls which taper toward convergence adjacent the first of saidtwo teeth.
 4. A strap as claimed in claim 1, wherein there is a thirdtooth on said pawl positioned intermediate between said first and secondtooth.
 5. A cable strap of unitary construction comprising an elongatedbody of generally rectangular cross section having ratched teeth with anenlarged head connected to one end of said strap, there being a passagethrough said head adapted to receive the looped end of the strap to forma loop for holding objects therein, the invention wherein within saidhead passage there is an elongated, flexible pawl integrally andcurvedly connected to said strap and extending freely into saidsidewalls, the body of said pawl comprising a smoothly curvedconcave-convex member of generally decreasing cross section and at leasta lower and upper tooth protruding from said pawl body adjacent the freeend thereof, said teeth spaced along said passage and spaced from andconfronting the end wall of the head, said pawl tapering from itsconnection to the strap to a narrowed section adjacent the lower of saidteeth, said pawl adapted to be flexed by said strap end to remove theupper tooth from contact with said strap end during movement of saidstrap through said head passage and said lower tooth protrusive fromsaid narrowed section to matingly engage said ratchet teeth as theremote end of the strap body is threaded through the passage, said uppertooth aligned to restore from said flexed position at the termination ofmovement of said strap through said passage, said upper tooth alignedopposite said end wall to restrain said strap against said end wall toprevent withdrawal of said strap from said passage.